Engineering molecular rotor-stator ligand architectures on copper nanoclusters for efficient photothermal conversion

Copper nanoclusters represent a promising yet underdeveloped frontier in materials science. Here, we propose a general and efficient strategy for enhancing photothermal conversion efficiency through the incorporation of rotor-stator ligand architectures onto copper nanocluster surfaces. As a representative example, we design carboxylate ligands functionalized with adamantane groups to stabilize a [Cu₃₆(4-F-PhS)₂₄(AdmCOO)₆(PPh₃)₄H₈]^2- nanocluster. In this architecture, the adamantane unit functions as a molecular rotor, while the carboxylate group serves as a molecular stator. The engineered nanocluster achieves a photothermal conversion efficiency of 75%. The adamantane rotors exhibit a lowered rotational energy barrier within the cluster framework, enabling stable and rapid molecular rotation that effectively promotes non-radiative transitions. This mechanism optimizes the conversion of light into thermal energy, enabling the nanocluster to rapidly heat up to 200 °C under 445 nm laser irradiation at a power density of 1.0 W cm^-2. The proposed strategy could be applicable to other rotor types, yielding a broad family of copper nanoclusters with enhanced photothermal conversion capabilities and multifunctional potential.